Documentation

The main filter for selecting parts of a document via XPath.
The string argument must be a XPath expression with an absolute location path,
the argument tree must be a complete document tree.
Result is a possibly empty list of XmlTrees forming the set of selected XPath values.
XPath values other than XmlTrees (numbers, attributes, tagnames, ...)
are convertet to text nodes.

The main evaluation entry point.
Each XPath-Expr is mapped to an evaluation function. The Env-parameter contains the set of global variables
for the evaluator, the Context-parameter the root of the tree in which the expression is evaluated.